“Refrigerant is the media (fluid) used for heat transfer in a refrigerating system that absorbs heat during evaporation from the region of low temperature and pressure, and releases heat during condensation at a region of higher temperature and pressure.”

1. REFRIGERANTS
IN REFRIGERATION AND AIR-
CONDITIONING
By
ANKIT SAXENA

2. REFRIGERANTS?
“Refrigerant is the media (fluid) used for heat transfer in a
refrigerating system that absorbs heat during evaporation
from the region of low temperature and pressure, and
releases heat during condensation at a region of higher
temperature and pressure.”

3. Classification of refrigerants

4. Primary Refrigerants
 These are the refrigerants which cools the substance or space
directly by absorbing latent heat.
 It absorbs heat during evaporation in the evaporator and
releases heat energy during condensation in condenser.
 It is also known as direct expansion system eg. Ammonia,
Freon, SO2, CO2 etc.
 These fluids provide refrigeration by undergoing a phase
change process in the evaporator.

5. Classification Of Primary Refrigerant
 Halo-carbon Refrigerant
 Azeotrope Refrigerant
 Inorganic Refrigerant
 Hydro-carbon Refrigerant

6. Halocarbon Refrigerants
 Halocarbon Refrigerant are all synthetically produced and were developed as the
Freon family of refrigerants.
 They are fluorocarbons of methane and ethane series.
 They contain 1 or more of these halogens (chlorine, bromine, fluorine)
 Non toxic, non-flammable, non-explosive, non- corrosive, non-irritant to human
body and eyes.
 Odourless, colourless
 Will not react with food product stored in the refrigerated space.
 Will not react with lubricating oil.
 Has excellent thermodynamic properties
 Only disadvantage is ozone layer is damaged.
Examples :
CFC’s : R11, R12, R113, R114, R115
HCFC’s : R22, R123
HFC’s : R134a, R404a, R407C, R410a

7. Azeotrope Refrigerants
 This group of refrigerants consist of mixture of different
refrigerants which can not separated under pressure and
temperature and have fixed thermodynamic properties.
 A stable mixture of two or several refrigerants whose vapour
and liquid phases retain identical compositions over a wide
range of temperatures.
 Azeotropic mixtures are designated by 500 series.
Examples :
R-500 : 73.8% R12 and 26.2% R152
R-502 : 8.8% R22 and 51.2% R115
R-503 : 40.1% R23 and 59.9% R13

8. Zeotropic Refrigerants
zeotropic mixture is one whose composition in liquid
phase differs to that in vapour phase. Zeotropic
refrigerants therefore do not boil at constant
temperatures unlike azeotropic refrigerants.
zeotropic refrigerants (e.g. non-azeotropic mixtures)
are designated by 400 series.
Examples :
R404a : R125 /R143a /R134a (44%,52%,4%)
R407c : R32/R125/R134a (23%, 25%, 52%)
R410a : R32/R125 (50%, 50%)
R413a : R600a/ R218/R134a (3%, 9%, 88%)

9. Hydrocarbons
 Most of the hydrocarbon refrigerant are successfully used in
industrial and commercial installation . They possess
satisfactory thermodynamic properties but are highly
flammable and explosive.
 Growing use in very small commercial systems like car air
conditioning system
Examples:
R170, Ethane, C2H6
R290 , Propane C3H3
R600, Butane, C4H10
R600a, Isobutane, C4H10
Blends of the above Gases

10. Secondary Refrigerants
 In refrigeration plant a secondary coolant is used as cooling medium which absorb
heat from refrigerated space and transfer to primary refrigerant in evaporator.
Substances that take away heat from the medium to be cooled and give it to the
boiling refrigerant are called secondary refrigerants
 They do not change their physical condition
 Secondary refrigerants are also known under the name brines or antifreezes.
 The refrigerants are brine which is used as intermediate fluid between evaporator
and the substance or space to be cooled. They cool the substance and the space by
absorbing their sensible heat. Also called indirect expansion system.
Eg. Brine solution made of calcium chloride or sodium chloride
 Water cannot be used as secondary refrigerant because at itself it will become
ice and circulation is not possible
 In brine solution CaCl2 is much preferred, it is very costly
0 C•

11. Designation of refrigerants
Since a large number of refrigerants have been developed
over the years for a wide variety of applications, a numbering
system has been adopted to designate various refrigerants.
From the number one can get some useful information about
the type of refrigerant, its chemical composition, molecular
weight etc. All the refrigerants are designated by R followed
by a unique number.

12. Fully saturated, halogenated compounds
• These refrigerants are derivatives of alkanes (CnH2n+2) such as methane
(CH4), ethane (C2H6). These refrigerants are designated by R XYZ, where:
• X+1 indicates the number of Carbon (C) atoms
• Y-1 indicates number of Hydrogen (H) atoms,
• Z indicates number of Fluorine (F) atoms
• The balance indicates the number of Chlorine atoms.
• Only 2 digits indicates that the value of X is zero.
Ex: R 22
• X = 0 No. of Carbon atoms = 0+1 = 1 derivative of methane (CH4)
• Y = 2 No. of Hydrogen atoms = 2-1 = 1⇒
• Z = 2 No. of Fluorine atoms = 2⇒
• The balance = 4 – no. of (H+F) atoms = 4-1-2 = 1 No. of Chlorine⇒
atoms = 1
∴The chemical formula of R 22 = CHClF2
Similarly it can be shown that the chemical formula of:
• R12 = CCl2F2
• R134a = C2H2F4 (derivative of ethane)

13. Inorganic refrigerants
These are designated by number 7 followed by
the molecular weight of the refrigerant
(rounded-off).
ex.:
1. Ammonia: Molecular weight is 17, the designation is R 717
2. Carbon dioxide: Molecular weight is 44, the designation is
R 744
3. Water: Molecular weight is 18, the designation is R 718

14. Thermodynamic properties of refrigerant
 Boiling and condensing temperature and pressures
 Freezing temperature
 Critical temperature
 Discharge temperature
 Latent heat of vaporisation
 Specific heat
 Density
 Viscosity

15. Boiling and condensing temperature and pressures
 The boiling temp of refrigerant at atmospheric pressure should be low. The
evaporator and condensing temperatures determine the pressures
 The maximum condensing temperature is largely affected by climatic condition
 It is desirable to select a refrigerant whose saturation pressure (at min. operating
temperature) is a few pounds above atmospheric pressure.
 If the boiling temperature of the refrigerant is high at atmospheric pressure
then compressor has to operate at high vacuums.
 Both evaporator and condenser pressure should be positive and it should be
near to atmospheric pressure.
Refrigerant R 11 R12 R21 R22 R30 R40 R113 R717
Boiling
Temperature at
atm pressure
21.77 -29 9 -41 39.8 -23.7 47.6 -10

16.  Freezing temperature
Should have low freezing temperature. Since the freezing temperature of most
of refrigerant is below -35
 Critical temperature
Should be well above the maximum condensing temperature
 Discharge temperature
High discharge temperatures from the compressor should be avoided It causes
some refrigerant breakdowns as well as poor lubrication effectiveness
 Latent heat of vaporization
Heat which converts the refrigerant from the liquid state to vapour
It should have a higher value
 Density
Low vapour density refrigerants are preferred
 Viscosity
Low viscosity of the liquid refrigerant is desired to reduce the pressure drop in
the lines
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18. Chemical properties of refrigerants
 Toxicity
Rated based on its effect on human beings over specified periods
Should be non toxic and non irritation
 Flammability and explosion Hazard
Should be non-flammable and non-explosive
 Refrigerant Odours
Can be both an asset and a hazard
Makes it easy to detect the leaks but at the same time may
contaminate foodstuffs in storage
Summary:
 Refrigerants should be non-flammable, non-explosive, not-toxic,
not react with lubricating oil, not react with moisture and should
not contaminate the food materials kept inside the refrigerating
system.

19. Environmental Effects of Refrigerants
Global warming :
 Refrigerants directly contributing to global warming when
released to the atmosphere
 Indirect contribution based on the energy consumption of
among others the compressors ( CO2 produced by power
stations)
Ozone depletion layer
Ozone layer gets depleted by the action of CFCs. The greatest
concentration of ozone are found from 12 km to 50 km above
the earth forming a layer in the stratosphere which is called
the ozone layer

22. The health and environmental concerns caused by the
breakdown of the ozone layer include:
•Increase in skin cancers
•Suppression of the human immune response system
•Increase in cataracts
•Damage to crops
•Damage to aquatic organisms
•Increase in global warming

23. Other important terms
a) Ozone Depletion Potential (ODP): According to the Montreal
protocol, the ODP of refrigerants should be zero, i.e., they should
be non-ozone depleting substances. Refrigerants having non-zero
ODP have either already been phased-out (e.g. R 11, R 12) or will
be phased-out in near-future(e.g. R22). Since ODP depends
mainly on the presence of chlorine or bromine in the molecules,
refrigerants having either chlorine (i.e., CFCs and HCFCs) or
bromine cannot be used under the new regulations.

24. b) Global Warming Potential (GWP): Refrigerants should have as
low a GWP value as possible to minimize the problem of global
warming. Refrigerants with zero ODP but a high value of GWP
(e.g. R134a) are likely to be regulated in future.
c) Total Equivalent Warming Index (TEWI): The factor TEWI
considers both direct (due to release into atmosphere) and
indirect (through energy consumption) contributions of
refrigerants to global warming. Naturally, refrigerants with as a
low a value of TEWI are preferable from global warming point of
view.